1. Field of the Invention
The present invention relates to a sewing machine that transfers the needle thread drawn from a thread supply with a thread transferring mechanism to hook the needle thread onto a plurality of thread hook sections such as needle bar thread guide etc. with an automatic thread hooking device.
2. Description of the Related Art
In a conventional sewing machine, the needle thread drawn from a thread spool is hooked onto a plurality of thread hooking sections (thread tension regulator, check spring and thread take-up, needle bar thread guide etc.) in a predetermined sequence and path and ultimately transferred to the sewing needle attached to the needle bar. The needle thread is then automatically passed through an eye of a sewing needle and sewing can be started. In case the sewing machine is provided with a threading mechanism, automatic threading is performed to pass the thread through the eye.
Various types of sewing machines have been reduced to practice in which the needle thread drawn from the thread spool is manually hooked onto a plurality of predetermined thread hooking sections on starting the sewing process, while sewing machines have been suggested, in which the needle thread is automatically hooked onto the needle bar thread guide provided on the lower end of the needle bar specifically as a thread hooking section.
For example, the thread hooking device for the thread guide described in JP-A-2004-65323 comprises a base member in the lower portion of the head, a movable member, a rotating arm, a hook member pivotably attached below the moveable member etc. In the thread hooking device so arranged, when the user inserts the cassette to the attachment, the downward operation of the thread cassette induces the threading of the eye. In the threading process, a hook member is shifted from the first stand-by position to the operation position by the first swing and engaged to the needle thread. Then the hook member slides to hook the needle thread onto the needle bar thread guide and returns to the second stand-by position by the second swing.
Because the threading device described in the above patent is configured with numerous members such as the base member, movable member, rotatable arm and the hook member, the thread hooking device suffers from increased size and installation complexity. Furthermore because the hook member in the thread hooking device not only rotates horizontally but slides as well, large space is required in the lower end of the needle bar, which is another problem. Yet furthermore, in case the thread hooking device is applied to a sewing machine that does not use a thread cassette, a separate drive source to horizontally rotate and slide the hook member is required, which demands even larger installing space and increased cost.